1. Field of the Invention
The present invention relates to a method and system for detecting trouble in a single-fiber two-way optical transmission. Recently, two-way optical transmission through a single optical fiber by using optical signals of the same or different wave lengths, is being developed in order to increase the amount of information transmitted through a single fiber. However, conventional methods for detecting trouble used in single-fiber one-way transmission, cannot be used in single-fiber two-way optical transmission.
2. Description of the Related Art
In the conventional single-fiber one-way transmission system, two-way transmission between two opposite optical terminal stations can be performed through at least two optical fibers in opposite directions. In such a system, the detection of trouble is carried out by monitoring at each optical terminal station the level of an optical signal transmitted through the optical fiber directed to the optical terminal station and received at the optical terminal station, and transmitting to the opposite optical terminal station an alarm signal for informing detection of trouble when an abnormality (failure) in the level of the optical signal is detected.
However, in the single-fiber two-way optical transmission systems, when trouble such as a break in the optical fiber occurs, an optical signal transmitted from an optical terminal station may be reflected at the point of the break, and then may be received by the optical terminal station which has transmitted the optical signal. Namely, in the single-fiber two-way optical transmission systems, trouble occurring in optical fibers may not be able to be detected by each optical terminal station by monitoring the level of the optical signal received at the optical terminal station.